Wind power is becoming increasingly popular due to its clean and environmentally friendly production of energy. The rotor blades of modern wind turbines capture kinetic wind energy by using sophisticated blade design created to maximize efficiency. Turbine blades may today exceed 80 metres in length and 4 metres in width. The blades are typically made from a fibre-reinforced polymer material and comprise a pressure side shell half and a suction side shell half. The cross-sectional profile of a typical blade includes an airfoil for creating an air flow leading to a pressure difference between both sides. The resulting lift force generates torque for producing electricity.
Transporting wind turbine blades from a production site to a wind power plant requires many transportation steps. Typically, the blades are transported by truck, train or ship and again by truck to the site of the wind power plant. Additionally, reloading between the different types of transportation is needed. Finally, the blades are stored at the production facility and at the site of the wind turbine power plant. Due to the size and fragility of large rotor blades, the blades may be damaged during transport as well as during loading and unloading. Such damage may seriously degrade the performance of the blades. Therefore, the blades need to be carefully packaged in order to ensure that they are not damaged.
In view of the increasing dimensions of modern wind turbine blades, it is becoming more challenging and costly to transport the blades. Transportation costs may amount to as much as 20 percent of the total costs for manufacturing, transporting and mounting the wind turbine blade on the rotor of a wind turbine blade. In addition, some blades are transported to the wind power plant using different modes of transport, such as by truck, train and ship. Some of these modes of transports may have restrictions on large loads, maximum heights, maximum widths, maximum distances between transport frames or supports, for instance dictated by local regulations. Therefore, there exists a logistic problem of providing transport solutions that are suitable for various types of transport.
Overall, there is a demand for making transport solutions simpler, safer and cheaper. In particular, there is a demand for making such systems more flexible such that adaption to a certain transportation situation is possible. This applies for example to shifting from land transport to sea transport. While height restrictions require lowest possible inter-blade spacings, sea transport may require an increased inter-blade spacing to avoid contact between blades during sea disturbance.
WO 2014/064247 describes a transportation and storage system for at least two wind turbine blades. The system is adapted to stack the blades in an alternating root end to tip end arrangement. The tip end of the second wind turbine blade may extend beyond the root end of the first wind turbine blade, and the tip end of the first wind turbine blade may extend beyond the root end of the second wind turbine blade, when the first and the second wind turbine blades are arranged in the packaging system.
EP1387802 discloses a method and system for transporting two straight wind turbine blades, where the root end of a first blade is arranged in a first package frame, and the tip end of a second, neighbouring blade is arranged in a second package frame that is arranged next to and connected to the first package frame with the effect that the blades are stored compactly alongside each other in a “tip-to-root” arrangement. However, in this transport system the tip end frames support the blades at the very tip of the blades, where they are mechanically most fragile. Further, the package frames are arranged at the root end face and the blade tip. Therefore, the distance between the package frames are approximately equal to the length of the blades. For very long blades of 45 metres or longer, this might not be possible due to local regulations and restrictions on transport.
Using some of these prior art approaches for transporting and/or storing increasingly larger wind turbine blades involves the challenge of providing a structure having low weight and high flexibility while maintaining a high standard of structural stability and safety.
It is therefore a first object of the present invention to provide a transportation and storage system for wind turbine blades which overcomes or ameliorates at least one of the disadvantages of the prior art or which provides a useful alternative.
Particularly, it is an object of the present invention to provide a transportation and storage system that is sufficiently light, yet mechanically stable.
It is another object of the present invention to provide a transport and storage solution that is simple and cost-efficient.